1. Field of the Invention
The present invention relates to an image capturing apparatus, an image capturing method, and a computer program for capturing an image including a photographic subject, such as a person, and more particularly, to an image capturing apparatus, an image capturing method, and a computer program for performing image capturing control in accordance with recognition of a specific pattern in a photographic subject included in an image.
More specifically, the present invention relates to an image capturing apparatus, an image capturing method, and a computer program for performing image capturing control on a captured image including multiple persons, and more particularly, to an image capturing apparatus, an image capturing method, and a computer program for performing image capturing control on the basis of the correlation between results of recognition of faces of multiple persons.
2. Description of the Related Art
In recent years, in place of silver salt cameras that capture images using films or sensitive plates, digital cameras that capture images using a solid-state image pickup device in which a light receiving section with an array of pixels performing photo-electric conversion and accumulation is implemented by a photodiode, perform digital coding processing on the captured images, and saves the processed images have been widely spread. As a solid-state image pickup device, for example, a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) device can be employed. For example, a CMOS sensor has advantages over a CCD sensor in that the CMOS sensor has small power consumption, the CMOS sensor is driven using a single low voltage, and the CMOS sensor is easily integrated with peripheral circuits.
The basic camera work of silver salt cameras is substantially the same as that of digital cameras. Combined with digitization of a captured image, automation has been extended to the camera work. Therefore, even an inexperienced user who is not good at operating a camera is significantly less likely to fail in capturing an image.
A major image capturing control function generally performs processing in accordance with at least one photographic subject existing in an image frame. In the past, a user manually entered settings relating to specify an important photographic subject. In recent years, an image capturing technique that employs face detection, such as detecting a face in a captured image, and automatically adjusting the focus to the detected face or automatically correcting image quality in accordance with the detected face, has been introduced. As a method of detecting a face in a captured image, for example, a method of matching an input image signal with an averaged face image serving as a template has been widely used (for example, see Japanese Unexamined Patent Application Publication No. 2003-271933 (paragraphs 0051 to 0053, FIG. 9)).
Recently, research and development of automatic image capturing in which an image capturing timing is determined using detection of a specific pattern, such as a smiling face, in an image of a photographic subject has been carried out. For example, a camera that determines whether, in a part of interest included in a main photographic subject of an image to be captured, the main photographic subject satisfies a predetermined image capturing condition and, if the predetermined image capturing condition is satisfied, outputs an image capturing timing signal has been proposed (for example, see Japanese Unexamined Patent Application Publication Nos. 2000-347278, 2004-294498, and 2006-237803). Specific criteria for determining an image capturing timing include, for example, “no blinking”, “eyes are looking toward the camera”, and “smiling”, which are conditions for capturing an attractive image of a person. Photograph retouching has been done for a long time. It is difficult to retouch a photograph of a person who is blinking to make it look as if the person is not blinking, or to retouch a photograph of a person who is not smiling to make it look as if the person is smiling. These difficulties are one of the reasons why these conditions are used as criteria for determining an image capturing timing. For example, whether a photographic subject satisfies the photographic condition “smiling” can be determined on the basis of image information indicating, for example, the area of a white portion of the eyes, the horizontal length of the mouth, and the area of a white portion in the mouth of the photographic subject.
An image capturing control method of, when two or more photographic subjects are included in a captured image, performing image capturing control by performing focusing or image quality correction on the basis of a specific photographic subject determined to be a “main character” has been conceived. Intuitively, a photographic subject positioned near the center of the captured image or a photographic subject occupying a large portion of the captured image is more significant and can be estimated as a main character. For example, a face-significance determining apparatus that more accurately determines significance for a photographer by obtaining size information and position information of a face detected in an image signal, computing a first significance factor on the basis of the size information, computing a second significance factor on the basis of the position information, and computing the final degree of significance on the basis of the first and second significance factors has been proposed (for example, see Japanese Unexamined Patent Application Publication No. 2007-201980).
Also, an image capturing control method of, when two or more photographic subjects are included in a captured image, performing image capturing control based on the correlation between the photographic subjects is conceived. An image capturing apparatus that recognizes, for example, the faces of multiple photographic subjects, organizes the photographic subjects into groups on the basis of image capturing parameters, such as the distance between the faces of the photographic subjects and the luminance of the photographic subjects, and sets optimal image capturing parameters for the individual groups, thereby capturing an image using the optimal image capturing parameters for the individual photographic subjects has been proposed (for example, see Japanese Unexamined Patent Application Publication No. 2006-345254).